Exam One - Spinal Cord Flashcards
What can damage to the spinal cord lead to?
altered sensation and loss of motor function
What are the 3 layers of the developing spinal cord?
Ependymal
Mantle
Marginal
What is the significance of the ependymal layer?
lines the central canal
What is the significance of the mantle layer?
In the grey matter
Alar plate: sensory
Basal plate: motor
Why is the sulcus limitans important?
separates the alar and basal plate in the mantle layer
What is the significance of the marginal layer?
white matter of the developing spinal cord
At what point in development does the sulcus limitans form?
4th week
Is alar plate sensory or motor? anterior or posterior horn?
sensory, posterior horn
Is basal plate sensory or motor? anterior or posterior horn?
motor, anterior horn
The SC develops from the _______ portion of the neural tube
caudal
Rachischisis
- the posterior neuropore fails to close by embryonic day 27
- undifferentiated neuroectoderm remains exposed
- accompanies cranial neural tube defects such as anencephaly, acrania, and myleomeningocele
Rachischisis is the more severe subtype of ______________
spina bifida cycstica
Where is the origin of the spinal cord?
foramen magnum
What level is considered the end of the spinal cord?
L1-L2
True or False? The spinal cord has no clear anatomical segmentation but a strong functional segmentation
True
Where do spinal nerves exit the vertebral column?
Through the intervertebral foramina
What is the last section of the sacral spinal cord called?
conus medullaris
What is the area beneath the conus medullaris called?
cauda equina
How many spinal cord segments are there?
31 total
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
True or False? Each pain of nerves exits the vertebral column at the level with which it lined up at birth
True
At what point in utero does the spinal cord and vertebral column have roughly the same length and the lower spinal nerves are directly opposite their respective intervertebral foramina?
12 weeks
C4 dermatome
shoulders
C5 derm
lateral upper arm
C6 derm
radial forearm, thumb
C7 derm
Middle finger
C8
ulnar, hand, little finger
T4
nipple
T10
umbilicus
L1
groin
L3
knee
L5
dorsal foot, big toe
S1
lateral foot, heel
S3-5
Genito-anal region
What level of the spinal cord has the thickest white matter? Grey matter?
White - cervical
Grey - sacral
Why does the cervical level have the most white matter?
most ascending fibers have already entered SC but most descending fibers have not yet exited the cord
Which level of SC has the least amount of grey matter?
thoracic
What is special about the thoracic level of SC?
has a lateral horn that contained intermediolateral cell columns at T1-2, mediates the entire sympathetic innervation to the body
Where are the two spinal cord enlargements?
cervical C4-T1 for arms
lumbar L1-3 for legs
grey matter: axons or soma?
soma
white matter: axon or soma?
axon
SC white matter 3 main divisions
posterior funiculus
lateral funiculus
anterior funiculus
What are the two subdivisions of the posterior funiculus in the cervical portion of the SC
gracile fasciculus (more medial)
cuneate fasciculus (more lateral)
gracile fasciculus
transmits information from the lower part of the body
cuneate fasciculus
transmits information from the upper part of the body
Lateral funiculus contains:
1 - lateral corticospinal tract (m)
2 - anterolateral system (s) (important for pain)
Anterior funiculus contains
reticulospinal, vestibulospinal, anterior corticospinal (m( and medial longitudinal fasciculus (MLF)
Anterior white commissure
fibers that cross the midline of the SC and transmit information from or to the contralateral side of the brain
What are the 3 zones of the SC grey matter
posterior zone
anterior zone
intermediate (lateral) zone
purpose of the posterior grey zone in SC
involved in sensory processing
purposes of the anterior grey zone in SC
contains the soma of lower motor neurons
(alpha-motor multipolar neurons)
purpose of the intermediate (lateral) grey zone in SC
contains the preganglionic sympathetic (thoracolumbar) and parasympathetic (sacral) neurons
nuclei of the dorsal zone grey matter
- nucleus posterior marginalis
- substantia gelatinosa
- nucleus proprius of post horn
nuclei of the intermediate zone of grey matter
- clarke’s nucelus (C8-L3 most prominent in low thoracic/lumbar segments. projects fibers into cerebellum)
- intermediolateral cell column (lateral horn, T2-L2, preganglionic sympathetic neurons)
- interomediomedial cell column (sacral levels S2-4, preganglionic parasympathetic neurons)
Lamina 1 associated with
nucleus posteromarginalis
lamina 2 associated with
substantia gelatinosa
lamina 3-6 associated with
nucleus proprius
lamina 7 associated with
nucleus proprius and clarke’s nucelus
lamina 8 associated with
intermediolateral and small interneurons of the ventral horn
lamina 9 associated with
lamina 10 associated with
Which laminae respond to pain?
laminae 1-5
what kind of pain information does laminae 1-2 receive?
receive information from alpha delta and C fibers
pain, thermal, and visceral stimuli
What kind of pain information does laminae 3-4 receive?
main targets of the large myelinated sensory alpha beta fibers from mechanoreceptors
What kind of pain information does laminae 5 receive?
respond to alpha beta and alpha delta (both painful and non-painful stimuli)
list nerve fiber types from most to least myelinated
alpha alpha
alpha beta
alpha delta (thin myelin)
c (unmyelinated/slowest conduction rate)
ventral horn is home to…
alpha motor neurons!
ventral horn contains
soma of motor neurons that send their axons out of SC via the ventral roots to innervate and control striated muscles
explain organization of ventral horn in regards to flexors, extensors, proximal, and distal
most anterior - extensors
most posterior - flexors
most medial - proximal/axial muscles
most lateral - distal muscles
all have some overlap in ventral horn except the flexors and extensors
ascending fiber tracts of the SC
dorsal: gracile and cuneate fasciculus
spinocerebellar tracts: ant/post
anterolateral system (ALS)
descending fiber tracts of the SC
lateral funiculus: lateral corticospinal, rubrospinal
anterior funiculus: medial reticulospinal, lateral vestibulospinal, anterior corticospinal, medial longitudinal fasciclus (MLF)
other fiber tracts…
ventral white commissure - connects left and right
posterolateral tract - small strand of fibers carrying pain and temp information. fibers ascend/descend 1-2 segments before entering gray matter
intrinsic tracts
fasciculus proprius (propriospinal)
- projects from one spinal level to another
- distributed in all 3 funiculi
role:
- integration of activity b/t R/L SC
- spinal cord functions as an integrated unit
hallmark signs of PN disorders:
- sensory impairment
- hyporeflexia
- weakness or flaccid paralysis
- hypotonus
- loss of autonomic functions (sweating, vasoconstriction/dilation, pilo-erection)
dermatome vs cutaneous fields
dermatome - an area of skin supplied by a single spinal nerve
cutaneous fields - an area of skin supplied by a specific peripheral sensory nerve
radiculopathy
- damage to nerve root
- DDD most common cause
- compression of single root may not cause significant sensory loss b/c overlap
- main symptoms: sharp, burning pain in dermatomal distribution of the spinal nerve
mononeuropathy
- deficits relect the distribution of a single anatomically defined peripheral nerve
- trauma is most common cause
What are the two major sources of blood supply to the spinal cord?
- branches of vertebral arteries: post/ant spinal arteries (& PICA)
- branches of segmental arteries: radicular arteries
What segmental branches supply the spinal cord?
- intercostal arteries in thorax
- lumbar arteries abdomen
- iliolumbar/lateral sacral in the pelvis
What branch supplies the ventral 2/3rd of the spinal cord?
ASA
ASA damage would be associated with _______ damage
motor
PSA damage would be associated with __________ deficits
sensory
What can damage the ASA?
Hyperextension
What symptoms are present if the ASA is occluded due to hyperextension?
- bilateral weakness arms, forearms, and hands
- patchy loss of sensation below the level of lesion
Syringomyelia
- cavitation that develops in central regions of SC and frequently affects anterior white commissure
- results in loss of pain and thermal sensation and muscle weakness that correlates with the damage level of SC
What is cauda equina?
nerve root involvement due to trauma, compression due to disc herniation or spinal stenosis, inflammation
What are symptoms of cauda equina?
- single or multi root involvement
- bilateral or unilateral
- low back pain, sciatica, loss/decrease in sensation, decreased muscle reflexes, bladder and bowel impairment, numbness in groin/perineum
cervical spondylosis
chronic compression of the SC and its associated spinal nerve roots
what is cervical spondylosis caused by
-intervertebral disc extrusion
- osteophytic outgrowth
what does cervical spondylosis result in?
- encroachment on the spinal cord
-ischemia - symptoms with neck movement
What are symptoms of cervical spondylosis
- painful/stiff neck
- arm pain and numb hands
- spastic lower extremities with unsteady gait
- paresthaesias (burning/prickling sensation) of distal limbs and trunk